well.let me help u out
as per my experience,a mc gets poor rating when he is not getting the ball or in other words not active in the match or he is being prone to counterattacks
1. ur first step shud be to get his morale to the maximum i.e. superb and let his condition bcum 100% and then make him play in the right postion in accordance to the foot i.e. if his right foot is his main,then he shud play as a right mc and vice versa.
2.if the first step fails,then u shud really make him sit for 5-6 matches.,then repeat the first step

hope it works or else its just ur bad luck